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Full text of "The Cambridge Natural History"

62                          INTESTINAL MEASUREMENTS                      CHAP.
structure. It is held by Gegenbaur that this organ is the
equivalent of the reptilian tongue, and that in the skeletal
vestiges which it contains are to be found the equivalents of the
hyoid skeletal cartilages which support the tongue in lizards.
In this case the tongue of mammals is a subsequently added
structure.
The oesophagus leads from the mouth cavity to the stomach.
The latter organ has commonly a distinctive shape in mammals.
This is well shown in Man. The orifices of the oesophagus and
intestine are somewhat approximated; and this causes a bulging
of the lower border of the organ, usually spoken of as the greater
curvature. A stomach of this typical form is found in many
orders of mammals, and is unlike the stomach in any of the
groups of lower vertebrates in shape. Sometimes the shape of
the organ is greatly altered: it may be drawn out, sacculated,
or divided, as in the Huminants and Whales, into a series of
differentiated chambers, each of which plays some special part in
the phenomena of digestion.
The intestine of mammals is always long and much coiled,
though the length and consequent degree of coiling naturally
varies. On the whole it is perhaps safe to say that it is shorter
in carnivorous than in vegetable-feeding beasts. Thus the Paca
has an intestine of 39 inches total length, while the Cat, an
animal of about the same size, has an intestine which is only
36 inches long. A fish diet, however, to judge from the Seals,
is associated with a long intestinal tract. The intestine is
divisible in. the vast majority of mammals into a small and a
large intestine. The two are separated by a valvular constriction
save in certain Carnivores; and in the majority of cases the
distinction is also emphasised by the presence at the junction of
a blindly-ending diverticulum, the caecum. This latter organ
varies greatly in length, being very short in the Cat-tribe and
exceedingly long in Bodents. Its size is, to some extent, de-
pendent upon the flesh-eating or grass-eating propensities pŁ
the animal in which it occurs. One of the longest caeca is
possessed by the Vulpine Phalanger, in which the organ is one-
fifth of the length of the small intestine; while the opposite
extremity is reached by Felis macroscelis, which lias a small
intestine one htuadred times the length of the caecum,
An interesting point in connexion with the gut of mammals